Co-seismic ruptures and deformations recorded by speleothems in the epicentral zone of the Basel earthquake.
Lemeille, F; Cushing, M; Carbon, D; Grellet, B; Bitterli, T; Flehoc, C; Innocent, C.
GEODINAMICA ACTA, 12: (3-4) 179-191.
The study of growth anomalies of speleothems in a karstic environment can provide potential evidence for palaeoearthquakes. These data are used to study the recurrence times of major earthquakes in areas where evidence for historic seismicity is lacking. A study has been carried out in the epicentral area of the 1356 Basel earthquake (epicentral intensity = VII-VIII, macroseismic magnitude = 6.2). The Battler loch and Dieboldslochli caves, situated in the area of greatest damage, show growth anomalies of speleothems possibly related to a seismic event (several breaks of speleothems and offsets of the axis of the regrowths). The first U/Th disequilibrium measurements by alpha spectrometry show recent ages (less than several tens of thousands of years and probably historic). C-14 dating by AMS of carbonate laminations taken on both sides of the anomalies confirm the evidence of a seismic event around 1300 AD. More accurate datings by U/Th TIMS are carried our in order to compare the information provided by the two different dating methods.